Suphedrin (pseudoephedrine HCl)

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Pseudoephedrine hydrochloride and sulfate are administered orally.

Pseudoephedrine hydrochloride 240-mg extended-release tablets should be administered orally once daily and swallowed whole with water; the extended-release tablets should not be divided, crushed, chewed, or dissolved. Patients should be advised that the tablet does not completely dissolve and may be passed in the stool.

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Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Mixed & Indirect Sympathomimetics; Oral Phenylephrine/Maois

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Catecholamine stores increased by MAOIs can be released by indirect acting sympathomimetics such as ephedrine and amphetamine. MAO inhibitors also interfere with gut and liver metabolism of direct acting sympathomimetics (e.g oral phenylephrine).

CLINICAL EFFECTS: Concurrent use of MAOIs may result in potentiation of sympathomimetic effects, which may result in headaches, hypertensive crisis, toxic neurological effects, and malignant hyperpyrexia. Fatalities have occurred.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of monoamine oxidase inhibitors and sympathomimetics is contraindicated. The manufacturers of sympathomimetic agents recommend waiting 14 days after discontinuation of MAO inhibitors before initiating the sympathomimetic.

DISCUSSION: Indirect acting sympathomimetic amines may cause abrupt elevation of blood pressure when administered to patients taking monoamine oxidase inhibitors, resulting in a potentially fatal hypertensive crisis. Mixed (direct and indirect) acting sympathomimetics have also been shown to interact with monoamine oxidase inhibitors depending on their degree of indirect action. The direct-acting sympathomimetics have not been reported to interact. Dopamine is metabolized by monoamine oxidase, and its pressor effect is enhanced by monoamine oxidase inhibitors. Linezolid is another antibacterial with monoamine oxidase inhibitor properties. Metaxalone is a weak inhibitor of MAO. Foods containing large amounts of tyramine have also been implicated in this interaction. Methylene blue, when administered intravenously, has been shown to reach sufficient concentrations to be a potent inhibitor of MAO-A. At recommended dosages, rasagiline, oral selegiline, and transdermal selegiline up to 6mg/day are selective for MAO-B; however, at higher dosages they have been shown to lose their selectivity. One or more of the drug pairs linked to this monograph have been included in a list of interactions that should be considered "high-priority" for inclusion and should not be inactivated in EHR systems. This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.

Sympathomimetics/Dihydroergotamine

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Concurrent use of dihydroergotamine and sympathomimetics may result in additive or synergistic effect on peripheral blood vessels.(1)

CLINICAL EFFECTS: Concurrent use of dihydroergotamine and sympathomimetics may result in increased blood pressure due to peripheral vasoconstriction.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Dihydroergotamine is contraindicated with sympathomimetics because the combination may result in additive or synergistic elevation of blood pressure.(1)

DISCUSSION: Significant elevation in blood pressure has been reported in patients treated with dihydroergotamine.(1) Sympathomimetics can be expected to have additional effects on blood pressure.

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Agents That Affect Catecholamines/Iobenguane I 123

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Many compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells.(1)

CLINICAL EFFECTS: Compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with imaging completed with iobenguane.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discuss the use of agents that affect catecholamines. Discontinue drugs that reduce catecholamine uptake or deplete catecholamine stores prior to imaging with iobenguane. Before imaging with iobenguane, discontinue agents that affect catecholamines for at least 5 biological half-lives, as clinically tolerated.(1)

DISCUSSION: Many agents may reduce catecholamine uptake or deplete catecholamine stores.(1) Examples include: - CNS stimulants or amphetamines (e.g. cocaine, methylphenidate, dextroamphetamine) - norepinephrine and dopamine reuptake inhibitors (e.g. phentermine) - norepinephrine and serotonin reuptake inhibitors (e.g. tramadol) - monoamine oxidase inhibitors (e.g. phenelzine, linezolid) - central monoamine depleting drugs (e.g. reserpine) - non-select beta adrenergic blocking drugs (e.g. labetalol) - alpha agonists or alpha/beta agonists (e.g. pseudoephedrine, phenylephrine, ephedrine, phenylpropanolamine, naphazoline) - tricyclic antidepressants or norepinephrine reuptake inhibitors (e.g. amitriptyline, bupropion, duloxetine, mirtazapine, venlafaxine) - botanicals that may inhibit reuptake of norepinephrine, serotonin or dopamine (e.g. ephedra, ma huang, St. John's Wort, yohimbine)

Agents That Affect Catecholamines/Iobenguane I 131

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Many compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells.(1)

CLINICAL EFFECTS: Compounds that reduce catecholamine uptake or that deplete catecholamine stores may impact the dosimetry calculations or effectiveness of iobenguane.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discuss the use of agents that affect catecholamines. Discontinue drugs that reduce catecholamine uptake or deplete catecholamine stores for at least 5 half-lives before administration of either the dosimetry or a therapeutic dose of iobenguane. Do not administer these drugs until at least 7 days after each iobenguane dose.(1)

DISCUSSION: Many agents may reduce catecholamine uptake or deplete catecholamine stores.(1) Examples include: - CNS stimulants or amphetamines (e.g. cocaine, methylphenidate, dextroamphetamine) - norepinephrine and dopamine reuptake inhibitors (e.g. phentermine) - norepinephrine and serotonin reuptake inhibitors (e.g. tramadol) - monoamine oxidase inhibitors (e.g. phenelzine, linezolid) - central monoamine depleting drugs (e.g. reserpine) - non-select beta adrenergic blocking drugs (e.g. labetalol) - alpha agonists or alpha/beta agonists (e.g. pseudoephedrine, phenylephrine, ephedrine, phenylpropanolamine, naphazoline) - tricyclic antidepressants or norepinephrine reuptake inhibitors (e.g. amitriptyline, bupropion, duloxetine, mirtazapine, venlafaxine) - botanicals that may inhibit reuptake of norepinephrine, serotonin or dopamine (e.g. ephedra, ma huang, St. John's Wort, yohimbine) - calcium channel blockers

Mixed & Indirect Sympathomimet; Oral Phenylephrine/Slt Maois

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Catecholamine stores increased by MAOIs can be released by indirect acting sympathomimetics such as ephedrine and amphetamine. MAO inhibitors also interfere with gut and liver metabolism of direct acting sympathomimetics (e.g oral phenylephrine).

CLINICAL EFFECTS: Concurrent use of MAOIs may result in potentiation of sympathomimetic effects, which may result in headaches, hypertensive crisis, toxic neurological effects, and malignant hyperpyrexia. Fatalities have occurred with combinations of sympathomimetics and MAO-A inhibitors.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of MAO-A inhibitors and sympathomimetics is contraindicated. The manufacturers of sympathomimetic agents recommend waiting 14 days after discontinuation of MAO inhibitors before initiating the sympathomimetic. Patients receiving indirect acting sympathomimetics should not receive linezolid unless they are monitored for potential increases in blood pressure. Initial dosages of dopamine should be reduced. At recommended dosages, oral selegiline and transdermal selegiline up to 6mg/day are selective for MAO-B; however, at higher dosages they have been shown to lose their selectivity. Patients receiving higher dosages of selegiline should be considered susceptive to this interaction.

DISCUSSION: Indirect acting sympathomimetic amines may cause abrupt elevation of blood pressure when administered to patients taking monoamine oxidase inhibitors, resulting in a potentially fatal hypertensive crisis. Mixed (direct and indirect) acting sympathomimetics have also been shown to interact with monoamine oxidase inhibitors depending on their degree of indirect action. The direct-acting sympathomimetics have not been reported to interact. Dopamine is metabolized by monoamine oxidase, and its pressor effect is enhanced by monoamine oxidase inhibitors. Foods containing large amounts of tyramine have also been implicated in this interaction. A significant pressor response was observed in normal subjects receiving linezolid and tyramine doses of more than 100 mg. Administration of linezolid (600 mg BID for 3 days) with pseudoephedrine (60 mg q 4 hours for 2 doses) increased blood pressure by 32 mmHg. Administration of linezolid (600 mg BID for 3 days) with phenylpropanolamine (25 mg q 4 hours for 2 doses) increased blood pressure by 38 mmHg. One or more of the drug pairs linked to this monograph have been included in a list of interactions that should be considered "high-priority" for inclusion and should not be inactivated in EHR systems. This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.

Mixed & Indirect Sympathomimet;Oral Phenylephrine/Rasagiline

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Catecholamine stores increased by MAOIs can be released by indirect acting sympathomimetics such as ephedrine and amphetamine. MAO inhibitors also interfere with gut and liver metabolism of direct acting sympathomimetics (e.g oral phenylephrine).

CLINICAL EFFECTS: Concurrent use of MAOIs may result in potentiation of sympathomimetic effects, which may result in headaches, hypertensive crisis, toxic neurological effects, and malignant hyperpyrexia. Hypertensive crisis has been reported in patients taking recommended doses of rasagiline with sympathomimetic agents.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: At recommended dosages, rasagiline is selective for MAO-B; however, at higher dosages it has been shown to lose its selectivity. Patients receiving higher dosages of rasagiline should be considered susceptive to this interaction. Concurrent use should be approached with caution.

DISCUSSION: Indirect acting sympathomimetic amines may cause abrupt elevation of blood pressure when administered to patients taking monoamine oxidase inhibitors, resulting in a potentially fatal hypertensive crisis. Mixed (direct and indirect) acting sympathomimetics have also been shown to interact with monoamine oxidase inhibitors depending on their degree of indirect action. The direct-acting sympathomimetics have not been reported to interact. Dopamine is metabolized by monoamine oxidase, and its pressor effect is enhanced by monoamine oxidase inhibitors.

Sympathomimetics/Ergot Alkaloids

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of ergot alkaloids and sympathomimetics may result in additive or synergistic effect on peripheral blood vessels.

CLINICAL EFFECTS: Concurrent use of ergot alkaloids and sympathomimetics may result in increased blood pressure due to peripheral vasoconstriction.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: When possible, avoid the concurrent use of ergot alkaloids and sympathomimetics. If concurrent use is warranted, monitor blood pressure and for signs of vasoconstriction. Decreasing the dose of one or both drugs may be necessary.

DISCUSSION: There have been reports of severe vasoconstriction resulting in gangrene in patients receiving intravenous ergonovine with dopamine or norepinephrine.

Moderate Interaction: Assess the risk to the patient and take action as needed.

Sympathomimetics (Direct, Mixed-Acting)/Guanethidine

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Direct or mixed-acting sympathomimetics may inhibit uptake of guanethidine at the adrenergic neuron.

CLINICAL EFFECTS: Decreased antihypertensive effectiveness. Effects may be seen for several days after discontinuation of the direct or mixed-acting sympathomimetic.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid concomitant administration of these drugs. If both drugs are administered, adjust the guanethidine dose as needed based on blood pressure.

DISCUSSION: Documentation supports routine monitoring of this interaction. It should be noted that this interaction can occur quickly.

Sympathomimetics (Direct, Mixed-Acting)/Methyldopa

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Unknown.

CLINICAL EFFECTS: The pressor response to sympathomimetics may be increased.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Start with low doses of sympathomimetics and monitor blood pressure of patients during concurrent administration of sympathomimetics and methyldopa.

DISCUSSION: The pressor response to sympathomimetics has been reported to be increased during methyldopa administration. In addition to increased duration of pressor response, severe hypertension has been reported.

Sympathomimetics/Rauwolfia Alkaloids

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Reserpine depletes catecholamine stores within the peripheral vascular adrenergic nerve endings, thus indirect acting sympathomimetics are unable to trigger the release of catecholamines. The reserpine-induced catecholamine release increases sensitivity to the effects of direct acting sympathomimetics.

CLINICAL EFFECTS: Increased effects of direct acting sympathomimetics. Decreased effects of indirect acting sympathomimetics. Mixed acting sympathomimetics will show effects based on the predominance of either direct or indirect activity.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If these agents are administered concurrently, monitor blood pressure. The dose of the sympathomimetic may need to be adjusted.

DISCUSSION: This interaction has been well documented in animal studies and human case reports have confirmed the interaction. Reserpine has been shown to decrease the response to epinephrine administered for hypotension. Reserpine has also been shown to decrease the effectiveness of ophthalmic epinephrine, a direct acting sympathomimetic. Ophthalmic phenylephrine has been shown to decrease the hypotensive effects of reserpine.

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• Severe coronary artery disease
• Severe uncontrolled hypertension
• Urinary retention

• Angle-closure glaucoma
• Benign prostatic hyperplasia
• Diabetes mellitus
• Hypertension
• Hyperthyroidism
• Pheochromocytoma

• Kidney disease with reduction in glomerular filtration rate (GFr)
• Severe hepatic disease

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Rare or Very Rare

• Acute generalized exanthematous pustulosis
• Dyspnea
• Hallucinations
• Hypertension
• Ischemic colitis
• Posterior reversible encephalopathy syndrome
• Reversible cerebral vasoconstriction syndrome
• Seizure disorder
• Vomiting

More Frequent

• Headache disorder
• Insomnia

Less Frequent

• Agitation
• Anorexia
• Dizziness
• Drowsy
• Dysuria
• General weakness
• Nausea
• Nervousness
• Pallor
• Tachycardia
• Tremor

Rare or Very Rare

• Abdominal pain with cramps
• Cardiac arrhythmia
• Chest tightness
• Dyspepsia
• Excitement
• Hyperhidrosis
• Palpitations
• Symptoms of anxiety
• Syncope

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